Theoretical radii of transiting giant planets: The case of OGLE-TR-56b

We calculate radius versus age trajectories for the photometrically selected transiting extrasolar giant planet, OGLE-TR-56b, and find agreement between theory and observation, without introducing an ad hoc extra source of heat in its core. The fact that the radius of HD 209458b seems larger than the radii of the recently discovered OGLE family of extremely close-in transiting planets suggests that HD 209458b is anomalous. Nevertheless, our good fit to OGLE-TR-56b bolsters the notion that the generic dependence of transit radii on stellar irradiation, mass, and age is, to within error bars, now quantitatively understood.